1. Field of the Invention
This invention relates to a structure of a swing reduction gear assembly for use with a construction equipment of the upper structure revolving type, a cargo handling equipment and so forth.
2. Description of the Related Art
A swing reduction gear assembly of the type mentioned is conventionally installed, for example, in such a hydraulic shovel as shown FIG. 7. Referring to FIG. 7, the hydraulic shovel includes a lower structure 1, a swing bearing 2, an upper structure 3, and a swing reduction gear drive 4 mounted on the upper structure 3. The upper structure 3 is mounted for swinging motion on the lower structure 1 by means of, for example, such a swing device as shown in FIG. 8.
Referring to FIG. 8, the swing device generally denoted at 5 is composed of a lower face plate 6 of the upper structure 3, an outer race 8 and an inner race 10 of the swing bearing 2, an upper face plate 9 of the lower structure 1, and rolling bodies 13 of the swing bearing 2 such as steel balls interposed between the outer race 8 and the inner race 10 of the swing bearing 2.
The outer race 8 of the swing bearing 2 is securely mounted on a lower face of the lower face plate 6 of the upper structure 3 while the inner race 10 of the swing bearing 2 is securely mounted on the upper face plate 9 of the lower structure 1, and the outer and inner races 8 and 10 of the swing bearing 2 are assembled for rotation relative to each other by way of the rolling bodies 13. An internal gear wheel 11 is formed on an inner periphery of the inner race 10, and an oil tank 12 is formed between the internal gear wheel 11 and a central upper projection of a plate b secured to the upper face plate 9 of the lower structure 1 and is filled with oil for the lubrication of teeth of the internal gear wheel 11 and a pinion 7 of thw swing reduction gear drive 4. The swing reduction gear drive 4 is mounted on the lower face plate 6 of the upper structure 3 and the pinion 7 thereof is held in meshing engagement with the internal gear wheel 11 of the swing bearing 2. Consequently, when the pinion 7 is rotated, the upper structure 3 is swung by a reactive force to the force of rotation.
A relationship between the swing bearing 2 and the swing reduction gear drive 4 is shown more particularly in FIG. 9 which is an enlarged view substantially of an encircled, portion A of FIG. 8. Referring to FIG. 9, a sealing collar 15 is secured to a lower bearing 14 which is secured in turn to a casing body of the swing reduction gear drive 4. A retainer 17 is securely mounted at a lower end of the casing body 16 by means of a plurality of bolts 18 (only one is shown), and an oil seal 19 is fitted on an inner periphery of the retainer 17. The oil seal 19 has a lip portion 20 normally held in engagement with an outer periphery of the sealing collar 15. A liner member 21 is interposed between the lower bearing 14 and the retainer 17. A seal member 22 is fitted in an annular groove formed on an inner periphery of the sealing collar 15.
An output shaft a of the swing reduction gear 4 is supported for rotation around an axial line 0--0 on the casing body 16 by means of an upper bearing and the lower bearing 14, and the pinion 7 is integrated with the lower end of the output shaft a of the swing reduction gear drive 4.
Since the retainer 17 on which the oil seal 19 is fitted is securely mounted at the lower end of the casing body 16, the oil seal 19 is mounted on the upper structure 3 side. Meanwhile, since the sealing collar 15 on the upper face side of the pinion 7 is fitted on the output shaft a integrated with the pinion 7, it is rotated in an integrated relationship with the pinion 7. Since the sealing collar 15 is held in close contact over the entire outer periphery thereof with the lip portion 20 of the oil seal 19 and the seal member 22 is provided on the inner periphery of the sealing collar 15, leakage of lubricating oil from within the swing reduction gear drive 4 is prevented by them.
In the structure described above, starting and stopping of swinging motion of the upper structure 3, which is great in weight and hence in inertia, are entirely carried out through meshing engagement between the pinion 7 and the internal gear wheel 11 of the inner race 10. Consequently, a high load is applied to faces of mutually contacting teeth of the pinion 7 and the internal gear wheel 11. Besides, the faces of mutually contacting teeth are slidably moved relative to each other. Thus, in order to assure a high degree durability of the tooth faces the annular oil tank 12 is formed between the internal gear wheel 11 of the inner race 10 and the plate b and a suitable amount of oil is filled in the oil tank 12 to lubricate the tooth faces.
Meanwhile, the output shaft a of the swing reduction gear drive 4 is supported by means of the upper bearing and the lower bearing 14, and the inside of the swing reduction gear drive 4 including the bearings is held in a sealed condition and internal components therein are lubricated with a different lubricating oil. Therefore, the oil seal 19 is provided between the retainer 17 at the lower portion of the swing reduction gear drive 4 and the output shaft a which rotates in order to prevent flowing out of the lubricating oil from the swing reduction gear 4 and admission of foreign particles into the swing reduction gear drive 4 from the outside.
In the swing device described above, the oil seal and the pinion are located at comparatively near locations relative to each other in order to assure a high strength of the output shaft of the swing reduction gear. Further, since the pinion and the internal gear wheel are held in meshing engagement with each other in the oil tank filled with oil, such oil will be squeezed out from between mutually contacting teeth of the pinion and the internal gear wheel.
Then, the oil squeezed out to the oil seal side may push open the dust lip and the seal lip of the oil seal and be admitted into the casing of the swing reduction gear drive. Consequently, the oil from the gear teeth may be mixed with the lubricating oil in the swing reduction gear drive, which will deteriorate the performance of the lubricating oil. Further, as a result of such admission of the oil, the oil in the swing reduction drive will be increased in amount and may thus be spouted to the outside by way of an oil level gage hole or some other opening portions of the casing, which will have a bad influence on the swing reduction gear drive.